It's seems to be like that, most of the time when bitcoin move up chances that Alts will fall a little as holders will sell out fast, wanting to hold btc as an asset making sure that they will get much better value of investment to people who hold and wait.
but that way I thought it would be bad because they would only get a bit of bitcoin because the price continued to rise while the altcoin decreased.
some altcoins are rising, following the growth of bitcoin. but not many like that. most are slow.
It means we must really careful pick coin that really can give potential when bitcoin price on up trend like this. Maybe old coins that have a lot of users, i mean there are some users and investor who always change their coin after they think they profit with it. And the others is who really support coins that they hold.